Process of producing artificial filaments



Patented Apr. 7, 1936 PATENT OFFICE PROCESS OF PRODUCING ARTIFICIAL FILAMENTS Camille Dreyfus, New York, N. Y., and William Whitehead,

Cumberland, Md.,

assignors to Celanese Corporation of America, a corporation of Delaware No Drawing. Application June 25, 1929, Serial No. 373,685

7 Claims.

This invention relates to the preparation of artificial filaments containing derivatives of cellulose and relates more particularly to the making of artificial filaments, yarns, bristles, straw or the like by a wet spinning process.

An object of our invention is to prepare lustrous artificial filaments, yarns, bristles, straw and the like by a wet spinning process. Other objects of our invention will appear from the following detailed description.

In the wet spinning of filaments or yarns from solutions of organic derivatives of cellulose, such solutions are extruded through orifices into a bath containing a liquid that causes the precipitation of the derivative of cellulose from the spinning solution to form filaments. However the filaments thus formed are opaque, dull and lustreless owing to the penetration of the precipitating liquid into the filaments which causes a discontinuity of theoptical property. We have found that if the wet spinning is conducted in such a manner that an amount of residual solvent or latent solvent is left in the filament, and the filament then subjected to elevated tempera tures, the residual solvent or latent solvent causes the filament to assume a high lustre.

In accordance with our invention we prepare strong lustrous filaments, yarns, bristles, straw and the like from derivatives of cellulose by extruding solutions of the same through orifices into a precipitating bath, the solution of the derivative of cellulose being of such nature or the precipitation being carried out in such manner that there is left in the filaments, yarns or bristles an amount of solvent or latent solvent. The filaments, yarns or the like that are so formed are then subjected to heat, whereupon the solvent or latent solvent present causes the opaque and lustreless filaments or yarns to be converted into a transparent and lustrous form.

The material to be formed by our process may be in the nature of fine filaments which are extruded through fine orifices, and these filaments may be associated together to form yarns. If artificial bristles are to be made, orifices of larger size are employed in the spinning, while fine slits in metal caps, glass tubes or the like may be employed for spinning artificial straw.

While we prefer to employ organic derivatives of cellulose in making the filaments and the like, other derivatives of cellulose such as cellulose nitrate may be employed. Examples of organic derivatives of cellulose are organic esters of cellulose such *as cellulose acetate, cellulose formate, cellulose propionate and cellulose butyrate and cellulose ethers such as ethyl cellulose, methyl cellulose and benzyl cellulose.

In the preferred form of our invention, there is present in the solution of the derivative of cellulose being spun, a substance which is a solvent for the derivative of cellulose at elevated temperatures, which substance is not readily removable from the filaments or yarns by the precipitating bath, either because it is relatively insoluble therein or for other reasons. Such substance may or may not be a solvent for the derivative of cellulose at ordinary temperatures. Examples of such substances when water is used as a precipitating bath are ethylene dichloride, methylene chloride, methyl phenyl ketone (acetophenone), tetrachlorethane, triacetin or dibutyl tartrate. This substance may be added to solutions of the derivative of cellulose wherein the derivative of cellulose is dissolved in liquids which are of themselves solvents for the derivative of cellulose, or they may be employed to form a solvent in admixture with the other liquids employed. As an example of the latter case, cellulose acetate may be dissolved in a solvent mixture comprising ethyl or methyl alcohol and ethylene dichloride or methylene chloride neither of which is alone a solvent for the cellulose acetate, and upon extrusion of the solution into water, the alcohol is dissolved away, thus precipitating the filaments containing the derivative of cellulose and some methylene chloride or ethylene dichloride.

Any suitable solvent may be employed for preparing the spinning solution for the derivative of cellulose, examples of which are acetone, choloroform, mixtures of methylene chloride and ethyl or methyl alcohol, or mixtures of dichlorethylene and methyl or ethyl alcohol, depending upon the solubility characteristics of the specific derivative of cellulose employed. As to the precipitating bath, any suitable liquid that is a nonsolvent for the derivative of cellulose, but which dissolves or is miscible with at least part of the solvent may be employed. Examples of these are water or hydrocarbon such as benzene, toluene and their homologues or other coal tar hydrocarbons, and gasoline, kerosene or other petroleum hydrocarbons.

Instead of employing in the spinning solution solvents or latent solvents for the derivative of cellulose which are not soluble in the precipitating bath, ordinary spinning solutions may be employed, but the precipitation is carried out in such a manner that some residual solvent is left in the filaments, yarns, straws, bristles and the like. This may be done by restricting the length of the path of the filaments or yarns in a precipitating bath, or restricting the time of contact by increasing the speed, or both, so that residual solvent is left therein after they leave the precipitating bath.

The yarns, filaments, straw and the like as they leave the precipitating bath are opaque and lustrousless. To impart transparency to the same, they are subjected to elevated temperatures whereupon the precipitating liquid adhering to or absorbed in the same is driven off and the solvent or latent solvent because of its increased solvent power at elevated temperatures, causes the filaments, yarns, straw, bristles and the like to assume lustre and transparency.

The heating of the filaments and the like may be done in any suitable manner, such as by causing the same to contact along a suitable length with feed rolls, pipes, rods, plates, etc., which may be heated electrically, by steam or in any other suitable manner. By passing the filaments and the like between pressure rolls, at least one of which is heated, the necessary length of contact with the heating device may be shortened.

This heating of the filaments and the like may be performed upon the same immediately after they leave the precipitating bath, or the filaments may be first wound or wound and twisted prior to their being subjected to the heating treatment.

During the coagulation or precipitation of the filaments and the like, a stretch may be imparted to the same so that finer filaments and the like may be produced through relatively large jet orifices.

In order further to illustrate our invention but without being limited thereto, the following. specific examples are given.

Example I A spinning solution is prepared as follows:

Parts by weight Cellulose acetate 20 Ethylene dichloride 48 Methyl alcohol 32 Triacetin 10 The cellulose acetate is preferably dissolved in the mixture of ethylene dichloride and methyl alcohol to form a homogeneous solution and the triacetin is then added thereto. The mixture is filtered and spun through a jet having fine orifices into a bath containing water. The water precipitates the fine threads of spinning solution issuing from the orifices, and the threads are caught up and wound off at the rate of 100 meters per minute. Prior to the winding the threads are wound over or around hot rolls that are heated to a temperature of 90 to 100 C. Prior to contacting with the rolls, the threads or filaments are dull and lustreless, but after contact with the heated rolls they are clear and lustrous. This is due to the fact that the ethylene dichloride and triacetin are hardly removed by the precipitating bath and remain in the yarn and are absorbed strongly by the yarns at the elevated temperatures as the water of the precipitating. bath is driven off. The products thus formed are materially stronger, tougher and more pliable than products not receiving this heat treatment.

Example II A spinning solution is prepared by dissolving 1 part of an acetone soluble cellulose acetate, containing 54% by weight of combined acetic acid in 3 parts of a solvent mixture consisting of Parts by Weight Acetone 95 Methyl phenyl ketone 5 This solution is spun exactly as in Example I. The methyl phenyl ketone, which is not soluble in or appreciably removed by the precipitating bath, causes the yarn to become lustrous and optically continuous when it is subjected to the elevated temperatures.

Example III A spinning solution is formed by dissolving 1 part by weight of an acetone soluble cellulose acetate in 3 parts by weight of a solvent mixture consisting of:

Parts by weight Acetone 95 Diethylene glycol 5 This spinning. solution is extruded through orifices into a bath containing kerosene and the filaments thus formed are then passed around devices heated to approximately 125 C. The diethylene glycol, which is insoluble in kerosene, remains in the yarn and has sufficient solvent action at the elevated temperatures to cause the yarn to become optically clear and continuous and lustrous.

It is understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein, without departing from the spirit of our invention.

Having described our invention, what we claim and desire to secure by Letters Patent is:

1. Method of forming filaments and the like which comprises extruding a solution of an organic substitution derivative of cellulose, containing a substance having .a solvent power for said cellulose derivative at elevated temperatures only, through orifices into a precipitating bath which incompletely extracts said substance, and bringing the filaments formed thereby into contact with a heated surface.

2. Method of forming filaments and the like which comprises extruding a solution of cellulose acetate, containing a substance having a solvent power for cellulose acetate at elevated temperatures only, through orifices into a precipitating bath which incompletely extracts said substance, and bringing the filaments formed thereby into contact with a heated surface.

3. Method of forming filaments and the like which comprises extruding a solution of an organic substitution derivative of cellulose, containing a substance substantially insoluble in water and having a. solvent power for said cellulose derivative at elevated temperatures only, through orifices into a precipitating bath containing water, and bringing the filaments formed thereby into contact with a heated surface.

4. Method of forming filaments and the like which comprises extruding a solution of cellulose acetate, containing a substance substantially insoluble in water and having a solvent power for cellulose acetate at elevated temperatures only,

which comprises extruding a solution or cellulose acetate containing methyl phenyl ketone through orifices into an aqueous precipitating bath, and bringing the filaments formed therehy into contact with a heated. surface.

'7. Method of forming filaments and the like which comprises extruding a solution of cellulose acetate, comprising diethylene glycol, through orifices into a precipitating bath containing kerosene, and bringing the filaments formed. thereby 10 into contact with a heated surface.

CAMILLE DREYFUS. WILLIAM WHITEHEAD. 

